Wear the trousers

Meaning

Be in charge.

Origin

To be 'wearing the trousers' is to be the dominant member of a household. In the days that this phrase was coined that person was normally expected to be the husband and father. The only reason to employ the phrase at all was to relate it to a woman, with the implication that the normal order had been overturned and that a woman was dominant over her husband.

The phrase was known in the USA from the late 19th century. It probably originated there as printed reference to it elsewhere don't appear until well into the 20th century. The Manitoba Daily Free Press used the term in November 1880, in an article about the domestic life of White Indians and their squaws - who we would now call Native Americans:

"The squaws are very beautiful
and are as fond of ornaments as Indian
women usually are. The women are
called ladies and they sometimes wear
the trousers or boss the white Indians,
their husbands."